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Journal of Bacteriology, January 2000, p. 135-142, Vol. 182, No. 1
Biotechnology Center for Agriculture and the
Environment, Rutgers University, New Brunswick, New Jersey 08901-8520
Received 23 July 1999/Accepted 11 October 1999
A gene was cloned from Burkholderia cepacia DBO1 that
is homologous with Escherichia coli cysH encoding
3'-phosphoadenylylsulfate (PAPS) reductase. The B. cepacia
gene is the most recent addition to a growing list of cysH
homologs from a diverse group of sulfate-assimilating bacteria whose
products show greater homology to plant 5'-adenylylsulfate (APS)
reductase than they do to E. coli CysH. The evidence
reported here shows that the cysH from one of the species,
Pseudomonas aeruginosa, encodes APS reductase. It is able
to complement an E. coli cysH mutant and a cysC
mutant, indicating that the enzyme is able to bypass PAPS, synthesized
by the cysC product. Insertional knockout mutation of
P. aeruginosa cysH produced cysteine auxotrophy, indicating
its role in sulfate assimilation. Purified P. aeruginosa CysH expressed as a His-tagged recombinant protein is able to reduce
APS, but not PAPS. The enzyme has a specific activity of 5.8 µmol · min
0021-9193/0/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Identification of a New Class of 5'-Adenylylsulfate
(APS) Reductases from Sulfate-Assimilating Bacteria
1 · mg of
protein
1 at pH 8.5 and 30°C with thioredoxin supplied
as an electron donor. APS reductase activity was detected in several
bacterial species from which the novel type of cysH has
been cloned, indicating that this enzyme may be widespread. Although an
APS reductase from dissimilatory sulfate-reducing bacteria is known, it
shows no structural or sequence homology with the assimilatory-type APS
reductase reported here. The results suggest that the dissimilatory and
assimilatory APS reductases evolved convergently.
*
Corresponding author. Mailing address: Biotech Center,
Rutgers University, 59 Dudley Rd., New Brunswick, NJ 08901-8520. Phone: (732) 932-8165, ext. 326. Fax: (732) 932-0312. E-mail:
LEUSTEK{at}AESOP.RUTGERS.EDU.
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